276C NT or other new mapping required

Well I've finally managed to acquire another 276C - sold my last one ages ago and have missed it ever since. I understand that they now support CN (NT) mapping - so what's available how how do I acquire it. I'd prefer to have mapping actually sat on my PC as my broadband speed is sub 1mbps so downloads take far too long and if I have to do that every time I need to change the map set then I'll be pulling what little hair I have left out.

Thanks in advance.
Rich